JP4233387B2 - PNEUMATIC TIRE AND METHOD OF INSTALLING PNEUMATIC TIRE - Google Patents

Description

試験の結果から、本発明の適用された空気入りタイヤは、従来例に比較してブロックの耐久性に優れており、トラクション、横滑り、及びギャップ通過性に関しても高い性能を有していることが分かる。
【０１１３】
なお、後輪用の空気入りタイヤをラジアル構造（タイヤサイズ：ＭＣＲ １２０／９０Ｒ１８。ナイロンコードからなるラジアル構造のカーカスプライを１枚有し、アラミド繊維コードからなるベルトプライを２枚有する。）とし、同様の試験を実施したが、結果は全く同じであった。
【０１１４】
【発明の効果】
以上説明したように、本発明の空気入りタイヤ、及び空気入りタイヤの装着方法によれば、接地面内での陸部のエッジ効果を確保し、陸部の剛性を損なうこと無く、陸部付け根部分の耐クラック性を向上することができる、という優れた効果を有する。
【図面の簡単な説明】
【図１】本発明の一実施形態に係る前輪用の空気入りタイヤのトレッドの展開平面図である。
【図２】図１に示す空気入りタイヤの回転軸に沿った断面図である。
【図３】ブロックの斜視図である。
【図４】（Ａ）はブロックの側壁面を示す縦断面図であり、（Ｂ）はブロックの角部（稜線部分）の断面図である。
【図５】（Ａ）は第１溝壁部を通るブロックの踏面に平行な断面図であり、（Ｂ）は第２溝壁部を通るブロックの踏面に平行な断面図であり、（Ｃ）は円弧曲面を通るブロックの踏面に平行な断面図である。
【図６】他の実施形態に係る空気入りタイヤのブロックの断面図である。
【図７】試験に用いた従来例に係る空気入りタイヤのブロックの断面図である。
【図８】試験に用いた実施例（試験種４）に係る空気入りタイヤのブロックの断面図である。
【図９】（Ａ）は面取り前のブロックの斜視図であり、（Ｂ）は図９（Ａ）に示すブロックの９（Ｂ）−９（Ｂ）線断面図であり、（Ｃ）は面取り後のブロックの斜視図であり、（Ｄ）は図９（Ｃ）に示すブロックの９（Ｄ）−９（Ｄ）線断面図である。
【符号の説明】
１０Ｆ 空気入りタイヤ
１２ トレッド
１４ ブロック（陸部）
１６ 側壁面
１６Ａ 第１溝壁部
１６Ｂ 第２溝壁部
１６Ｃ 付け根曲面[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire and a method for mounting a pneumatic tire, and more particularly, to a pneumatic tire suitable for a motorcycle mainly used for rough terrain traveling and a method for mounting a pneumatic tire.
[0002]
[Prior art]
Cornering on rough terrain is one of the characteristics of motorcycle terrain tires with a large negative ratio, which is a particularly desirable application and requires a large load and stress concentration at the corner ridges of the tread surface. Performance, traction, and braking are very important requirements.
[0003]
Especially for racing tires used in motocross races, etc., high-speed cornering, acceleration with high traction, and sudden braking are performed, so the performance requirements of front and rear and left and right grips are very important. It has become.
[0004]
In order to improve these performances, it is an effective means to obtain an edge effect by making the side wall inclination angle of the block as close as possible to the tread surface as much as possible (see Non-Patent Document 1).
[0005]
However, as the side wall inclination angle of the block gets closer to the vertical, the rigidity of the block becomes weaker, and before the grip characteristics and traction characteristics are improved, problems such as tire twist (decrease in steering stability) occur. There is.
[0006]
Further, as the side wall inclination angle of the block is made closer to the vertical, the rigidity of the block is lowered, the movement of the block itself is increased, and the performance of the block is also deteriorated.
[0007]
On the other hand, in the production of a tire vulcanization mold (mold), a tread ring part for forming a tread surface pattern is first made in a model similar to a product with gypsum and the like, and a mold is made based on the model, Although there is an operation to make a modal tread ring, conventionally, in forming the model, as shown in FIGS. 9A and 9B, first, the side wall surface of the block is set to the angle surface (normal line HL of the tread surface). A flat surface with an angle (α) of a certain degree (several degrees) is formed, and then the base portion of the side wall surface is formed into an arc curved surface (radius r) smoothly connected to the groove bottom surface.
[0008]
Next, of the ridge lines formed by the sharp edges formed at the corners of the block by abutting the pair of side wall surfaces formed as described above, the vicinity of the root connected to the groove bottom (by the abutting of a pair of circular curved surfaces) As shown in FIG. 9 (C), a curved blurring, that is, a rounded chamfer 100, is attached to the ridgeline to avoid stress concentration at the bottom of the groove when it actually becomes a tire, and to prevent chipping of the block. I was taking a countermeasure.
[0009]
However, although there is a size of the appearance, by cutting the ridgeline, the shaved part is not less than the under volume (FIG. 9 (D) 9 (D) cross-sectional view of FIG. 9 (D) 9D, the solid line is the chamfer after chamfering, and the two-dot chain line is the one before chamfering.) Source).
[0010]
However, in the past, this has been inevitable in finishing the mold, and such a state has been approved.
[0011]
In order to ensure the chip resistance of the block, it is possible to take measures by increasing the inclination angle of the side wall of the block or by taking a large groove bottom R. However, the ridge line near the base of the block described above is chamfered. For this reason, it is a method contrary to cutting, and it has been extremely difficult to achieve a good balance between improvement in steering stability and chipping resistance of blocks and the like.
[0012]
In addition, it is an effective means to prevent block chipping by making the ridge line of the block into a rounded chamfer shape from the ground contact surface to the groove bottom, but the maximum edge effect is achieved as a pneumatic tire block for motorcycles for motocross racing. In order to ensure the limit, it is important that the tread shape is rectangular (the corner of the tread is a right angle and not chamfered), that is, has a sharp ridgeline. Therefore, cutting the ridge line from the ground contact surface to the groove bottom is a negative factor for a pneumatic tire for a motocross race, even though it is effective in preventing block chipping.
[0013]
[Non-Patent Document 1]
M401 (Front) and M402 (Rear) described in the Bridgestone Motocross & Enduro Tire catalog created in May 2002.
[0014]
[Problems to be solved by the invention]
The present invention was made to solve the above-mentioned problem, ensuring the edge effect of the land portion within the ground contact surface, and capable of taking measures against cracks at the base portion of the land portion without damaging the rigidity of the land portion. It is an object to provide a pneumatic tire.
[0015]
[Means for Solving the Problems]
The invention according to claim 1 is provided with a land portion defined by a plurality of grooves intersecting each other in a tread, and a ridge line is formed at a corner portion of the land portion formed by a side wall surface and a side wall surface adjacent to each other of the land portion. In the formed pneumatic tire, the groove bottom surface side of the side wall surface has an arcuate root curved surface having a center of curvature outside the land portion and smoothly connected to the groove bottom surface, A corner angle portion formed by a pair of root curved surfaces of the corner portions is formed in a substantially smooth curved chamfered shape, and the side wall surface excluding the root curved surface is defined as the land corner portion. , And the virtual ridgeline defined by the virtual side wall surface obtained by extending toward the groove bottom surface, or is located on the outside of the land portion.
[0016]
Next, the operation of the pneumatic tire according to claim 1 will be described.
[0017]
In the pneumatic tire according to claim 1, an arc-like root curved surface having a center of curvature outside the land portion and smoothly connecting to the groove bottom surface is formed on the groove bottom surface side of the side wall surface of the land portion. Since the base corner portion formed by a pair of base curved surfaces of the corner portions is formed in a substantially smooth curved chamfered shape, stress concentration near the boundary between the land portion and the groove bottom is relaxed, It is possible to prevent chipping of the land.
[0018]
In addition, the base corner portion of the land portion corner portion coincides with the virtual ridgeline defined by the virtual side wall surface obtained by extending the side wall surface excluding the base curved surface toward the land portion corner portion and the groove bottom surface or the land portion. Since it is located outside the section, the volume of the base portion of the land portion can be secured even if the base corner portion of the land portion is chamfered, and the rigidity of the land portion can be ensured.
[0019]
The invention according to claim 2 is the pneumatic tire according to claim 1, wherein the negative ratio of the tread is set within a range of 65 to 97%, and the tread width measured along the rotation axis of the tread is Tw, When the distance measured along the tire radial direction from the tire equatorial plane position on the tread surface of the tread to the tread end is TH, and TH / Tw is defined as the Tr curvature ratio, the Tr curvature ratio is 0.20-0. 50, and the side wall surface has a plurality of groove wall portions with different inclination angles with respect to the normal line perpendicular to the tread surface in the groove depth direction, and the groove wall surface from the ground side toward the groove bottom side When the inclination angle of the portion is α, α1, α2, α3... Αn-1, αn, the groove wall portion having the inclination angle αn connected to the root curved surface and the groove having the inclination angle αn-1 The wall portion satisfies the relationship of αn> αn−1, and Satisfying −10 ° ≦ α ≦ 20 °, αn ≧ α, and 0 ° ≦ αn ≦ 30 °, the height of the land portion is H, the groove wall portion having an inclination angle α and the inclination angle α1 The land portion angle formed by the groove wall portion satisfying 0.2H ≦ h ≦ 0.8H and at least the inclination angle αn, where h is the height of the boundary portion with the groove wall portion formed The portion is formed in a curved chamfer shape following the land corner portion formed by the root curve.
[0020]
Next, the operation of the pneumatic tire according to claim 2 will be described.
[0021]
By setting the inclination angle α of the groove wall portion closest to the ground side to −10 ° ≦ α ≦ 20 °, the edge effect of the ground end of the land portion can be sufficiently ensured. The positive inclination angle indicates that the groove wall portion is inclined such that the groove bottom side is closer to the groove center side than the tread surface side (as the groove, the tread surface side is wide and the groove bottom side is narrow). The negative inclination angle indicates that the inclination angle is in the opposite direction.
[0022]
By satisfying αn ≧ α, the land portion has a divergent shape, and high land portion rigidity is obtained.
[0023]
By setting 0 ° ≦ αn ≦ 30 °, high land portion rigidity can be obtained.
[0024]
Here, when the negative ratio of the tread is less than 65%, the effective ground contact area increases on a hard road surface, but conversely, the ground contact pressure in the land portion in the ground contact surface decreases and an effective edge effect cannot be obtained.
[0025]
On the other hand, if the negative ratio of the tread exceeds 97%, the minimum required ground contact area cannot be obtained, and the land portion becomes inevitably small, so that the land portion rigidity cannot be secured.
[0026]
Next, when the Tr curvature ratio is less than 0.20, a necessary bank angle cannot be secured (a flat shape). Also, when you ride the bike, the ground contact surface decreases from a certain angle.
[0027]
On the other hand, when the Tr curvature ratio exceeds 0.50, handling for turning back becomes heavy. In addition, the ground contact area during straight traveling is reduced, resulting in insufficient traction.
[0028]
Next, when αn <αn−1, the rigidity of the land portion of the base becomes lower than the rigidity of the surface layer portion, and cracks are likely to occur.
[0029]
Next, when 0.2H> h, necessary land portion rigidity cannot be obtained, and the entire land portion becomes weak.
[0030]
On the other hand, when 0.8H <h, the rigidity of the land portion of the tread surface portion becomes high, and steering stability cannot be obtained.
[0031]
Next, when −10 °> α, the rigidity of the tread portion is too weak, and the feeling of rigidity necessary for steering stability is insufficient.
[0032]
On the other hand, when α> 20 °, the edge effect is reduced and steering stability cannot be obtained.
[0033]
Next, when αn <α, the rigidity of the land portion of the base is lower than the rigidity of the surface layer portion, and cracks are easily generated.
[0034]
Next, when 0 °> αn, there is a possibility that the land portion lacks due to insufficient land portion rigidity.
[0035]
On the other hand, when αn> 30 °, the land portion rigidity becomes larger than necessary, and the steering stability cannot be obtained.
[0036]
According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, the negative ratio of the tread is set in a range of 75 to 97%, and the Tr curvature ratio is 0.23 to 0. ..45 is set within the range.
[0037]
Next, the operation of the pneumatic tire according to claim 3 will be described.
[0038]
When traveling on rough terrain, the straightness and handling characteristics of the front wheels are important. If it contacts more than necessary, it will be easy to receive the disturbance from a road surface, Therefore Compared with a rear wheel, a negative is large and a tread curvature tends to become small.
[0039]
From the above, if the negative ratio is in the range of 75 to 97%, when used for front wheels, the required ground contact area and land rigidity can be ensured, and the deterioration of straight running stability due to excessive ground contact area is prevented. I can do it.
[0040]
If the negative ratio of the tread is less than 75%, high performance can be obtained as compared with the conventional one, but the above-described action suitable as a front wheel cannot be obtained sufficiently.
[0041]
On the other hand, if the negative ratio of the tread exceeds 97%, it will not be possible to secure the required ground contact area and land rigidity for the front wheels.
[0042]
If the Tr curvature ratio is less than 0.23, the bank angle required for the front wheels cannot be secured (a flat shape). Also, when you ride the bike, the ground contact surface decreases from a certain angle.
[0043]
On the other hand, when the Tr curvature ratio exceeds 0.45, the handling of turning back becomes heavy, and the ground contact area when going straight becomes small, resulting in insufficient braking.
[0044]
According to a fourth aspect of the present invention, in the pneumatic tire according to the first or second aspect, the negative ratio of the tread is set in a range of 68 to 85%, and the Tr curvature ratio is 0.23 to 0. ..45 is set within the range.
[0045]
Next, the operation of the pneumatic tire according to claim 4 will be described.
[0046]
When traveling on rough terrain, the traction characteristics of the rear wheels, which are drive wheels, are important in comparison with the front wheels.
[0047]
By setting the negative ratio of the tread within the range of 68 to 85% and the Tr curvature ratio within the range of 0.23 to 0.45, a high traction characteristic preferable for rear wheels and a lateral grip can be obtained. It is preferable that the engine power can be efficiently transmitted to the road surface.
[0048]
When the negative ratio of the tread is less than 68%, high performance can be obtained as compared with the conventional one, but the above-described action suitable as a rear wheel cannot be obtained sufficiently.
[0049]
On the other hand, if the negative ratio of the tread exceeds 85%, the absolute ground contact area is insufficient, and the required steering stability cannot be obtained.
[0050]
If the Tr curvature ratio is less than 0.23, the bank angle required for the rear wheel cannot be secured (a flat shape). Also, when you ride the bike, the ground contact surface decreases from a certain angle.
[0051]
On the other hand, when the Tr curvature ratio exceeds 0.45, the ground contact area at the time of straight traveling becomes small, resulting in insufficient traction in the rear wheels as drive wheels.
[0052]
According to a fifth aspect of the present invention, in the pneumatic tire according to any one of the first to fourth aspects, the structure of the pneumatic tire is a radial structure.
[0053]
Next, the operation of the pneumatic tire according to claim 5 will be described.
[0054]
When the load of the radial structure is set to be equal, the tire mass can be reduced due to the characteristics of the tire structure as compared with the tire of the bias structure. As a result, it is advantageous in handling ease and reduction of unsprung load.
[0055]
Further, in the case of a radial tire, the grip characteristics of the tread portion are improved due to its structure, so that the strain that the land portion bears increases, which tends to be disadvantageous against the lack of the land portion compared to the bias tire. However, the application of the present invention makes it possible to achieve both improvement in steering stability and ensuring durability of the land.
[0056]
The pneumatic tire mounting method according to claim 6 is characterized in that the pneumatic tire according to claim 3 is used for a front wheel of a motorcycle and the pneumatic tire according to claim 4 is used for a rear wheel of the motorcycle. Yes.
[0057]
Next, a method for mounting the pneumatic tire according to claim 6 will be described.
[0058]
The operation when the pneumatic tire according to claim 3 is used for a front wheel of a motorcycle is as described above, and the operation when the pneumatic tire according to claim 4 is used for a rear wheel of a motorcycle is as described above. It is.
[0059]
By using pneumatic tires for the front and rear wheels of a motorcycle in this way, it is possible to ensure the edge effect of the land within the ground contact surface and to take measures against cracks at the base of the land without impairing the rigidity of the land. The maximum performance of motorcycles can be demonstrated.
The invention according to claim 7 is the pneumatic tire mounting method according to claim 6, wherein the pneumatic tire has a radial structure.
[0060]
Next, a method for mounting the pneumatic tire according to claim 7 will be described.
[0061]
By setting the tire structure to a radial structure, the tire mass can be reduced by the characteristics of the tire structure as compared with the tire of the bias structure when the load is set to be equal. As a result, it is advantageous in handling ease and reduction of unsprung load.
[0062]
Further, in the case of a radial tire, the grip characteristics of the tread portion are improved due to its structure, so that the strain that the land portion bears increases, which tends to be disadvantageous against the lack of the land portion compared to the bias tire. However, the application of the present invention makes it possible to achieve both improvement in steering stability and ensuring durability of the land.
[0063]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a motorcycle pneumatic tire according to an embodiment of the present invention will be described with reference to FIGS. 1 to 5.
(Pneumatic tire for front wheels)
FIG. 1 is a development view of a tread 12 of a pneumatic tire 10F used for a front wheel of a motorcycle. The tire structure of the pneumatic tire 10F of the present embodiment is a general bias structure, and the description of the internal structure is omitted.
[0064]
As shown in FIG. 1, the tread 12 of the pneumatic tire 10F has a plurality of rectangles defined by a circumferential groove extending along the tire circumferential direction (arrow A direction) and a widthwise groove extending along the tire width direction. The block 14 is provided.
[0065]
The negative ratio of the tread 12 needs to be set within a range of 65 to 97%, and is preferably set within a range of 75 to 97% for the front wheels.
[0066]
2, the tread width measured along the rotation axis of the tread 12 is Tw, the tire equatorial plane position P1 on the tread 12 tread edge 12E (the tire width direction of the outermost block in the tire width direction) When the distance measured along the tire radial direction to the outermost edge) is TH and TH / Tw is defined as the Tr curvature ratio, the Tr curvature ratio should be set within the range of 0.20 to 0.50. It is necessary, and it is preferable to set it within the range of 0.23 to 0.45 for the front wheels.
[0067]
As shown in FIG. 3, each side wall surface 16 of the block 14 of the present embodiment has a first groove wall portion 16A and a first groove wall portion 16A on the tread surface side, as shown in FIG. It is composed of a second groove wall portion 16B on the groove bottom surface side, and an arcuate root curved surface 16C having a radius r and having a center of curvature outside the block connected to the groove bottom surface 18.
[0068]
The block corners formed by the pair of first groove wall portions 16A are angular as shown in FIG. 5A, but the block corners formed by the pair of root curved surfaces 16C are shown in FIG. As shown in Fig. 4, a rounded chamfer (curvature radius R) is applied.
[0069]
Further, as shown in FIG. 5B, the block corner formed by the pair of second groove wall portions 16B also has a rounded chamfer (curvature radius R1) following the block corner formed by the pair of root curved surfaces 16C. ) Is given.
[0070]
FIG. 4B shows a longitudinal section along the corner of the block 14. As shown in FIG. 4B, a pair of root curved surfaces 16C with respect to the virtual ridgeline 20 defined by the virtual side wall surface obtained by extending the first groove wall portion 16A toward the block corner portion and the groove bottom surface. The block corner portion 16Ca formed by (1) and the block corner portion 16Ba formed by the pair of second groove wall portions 16B coincide with the virtual ridge line 20 or are located outside the virtual ridge line 20 in the block.
[0071]
As shown in FIG. 4A, in the present embodiment, the height H of the block 14 is 15 mm, the inclination angle α of the first groove wall portion 16A with respect to the normal HL perpendicular to the tread is 4 °, and the normal HL. The inclination angle α1 of the second groove wall portion 16B is set to 11 °, the height h of the boundary between the first groove wall portion 16A and the second groove wall portion 16B is set to 11 mm, and the curvature radius r of the root curved surface 16C is set to 5 mm. Yes.
[0072]
Further, as shown in FIG. 5C, the radius R of chamfering of the block corner portion 16Ca formed by the pair of root curved surfaces 16C is 2 mm, and as shown in FIG. 5B, the pair of second grooves The radius of curvature R1 of the rounded chamfer of the block corner portion 16Ba formed by the wall portion 16B is set to 1 mm.
(Pneumatic tire for rear wheels)
Although illustration is omitted, the tread of the pneumatic tire for the rear wheel of the motorcycle also has a block pattern and includes a block similar to the block 14 of the pneumatic tire 10F for the front wheel.
[0073]
In addition, as a pneumatic tire for rear wheels, it is preferable to set the negative ratio of the tread within a range of 68 to 85% and the Tr curvature ratio within a range of 0.23 to 0.45.
[0074]
In addition, the definition of the block shape is the same as that of the pneumatic tire 10F for the front wheels.
(Function)
In the front-wheel pneumatic tire 10F and the rear-wheel pneumatic tire of the present embodiment, the side wall surface 16 of the block 14 is formed with an arc-shaped root curved surface 16C on the groove bottom surface side, and a pair of root curved surfaces 16C. The block corner portion 16Ca formed by the step S16 and the block corner portion 16Ba formed by the second groove wall portion 16B on the tread surface side thereof are rounded so that stress concentration near the boundary between the block 14 and the groove bottom is reduced. As a result, the chipping of the block 14 can be prevented.
[0075]
Further, the block corner portion 16Ca formed by the pair of root curved surfaces 16C and the block corner portion 16Ba formed by the second groove wall portion 16B on the tread surface side, the first groove wall portion 16A is replaced by the block corner portion and the groove. Since it is located outside the block with respect to the virtual ridge line 20 defined by the virtual side wall surface obtained by extending toward the bottom surface, even if the corners of the block are rounded as in the present embodiment, the block 14 The volume near the root can be secured, and the block rigidity can be secured.
[0076]
When the Tr curvature ratio is less than 0.20, a necessary bank angle cannot be secured (a flat shape is obtained). Also, when you ride the bike, the ground contact surface decreases from a certain angle.
[0077]
On the other hand, when the Tr curvature ratio exceeds 0.50, handling for turning back becomes heavy. In addition, the ground contact area during straight traveling is reduced, resulting in insufficient traction.
[0078]
Next, when 0.2H> h, the required block rigidity cannot be obtained, and the entire block becomes weak.
[0079]
On the other hand, when 0.8H <h, the block rigidity of the tread portion increases, and steering stability cannot be obtained.
[0080]
Next, when −10 °> α, the rigidity of the tread portion is too weak, and the feeling of rigidity necessary for steering stability is insufficient.
[0081]
On the other hand, when α> 20 °, the edge effect is reduced and steering stability cannot be obtained.
[0082]
Next, when α1 <α, the rigidity of the land portion of the base is lower than the rigidity of the surface layer portion, and cracks are easily generated.
[0083]
Next, when 0 °> α1, there is a risk of block missing due to insufficient block rigidity.
[0084]
On the other hand, when α1> 30 °, the block rigidity becomes unnecessarily large, and steering stability cannot be obtained.
[0085]
Also, when traveling on rough terrain, the straightness and handling characteristics of the front wheels are important. If contact is made more than necessary, it is easy to receive disturbance from the road surface. Therefore, it is preferable to make the negative larger and the tread curvature smaller than the rear wheels. Therefore, as in the present embodiment, the negative ratio of the front wheel pneumatic tire 10F is set larger than the negative ratio of the rear wheel pneumatic tire 10F, and the negative ratio of the front wheel pneumatic tire 10F is 75 to It is preferable that the negative ratio of the pneumatic tire for the rear wheel is within the range of 68 to 85% within the range of 97%.
[0086]
Thereby, the pneumatic tire 10F can secure a ground contact area and a land portion rigidity necessary for a front wheel, and can prevent a decrease in straight running stability due to an unnecessarily large ground contact area.
[0087]
In the front wheel pneumatic tire 10F, when the negative ratio of the tread 12 is less than 75%, high performance can be obtained as compared with the conventional one, but the above-described operation suitable as a front wheel cannot be sufficiently obtained.
[0088]
In the front tire 10F, if the Tr curvature ratio is less than 0.23, the bank angle required for the front wheel cannot be secured (a flat shape). Also, when you ride the bike, the ground contact surface decreases from a certain angle.
[0089]
Further, in the pneumatic tire 10F for the front wheels, when the Tr curvature ratio exceeds 0.45, handling for turning back becomes heavy, and a ground contact area at the time of going straight becomes small, resulting in insufficient braking.
[0090]
When traveling on rough terrain, the traction characteristics of the rear wheels, which are drive wheels, are important in comparison with the front wheels. Therefore, in the pneumatic tire for rear wheels, it is preferable to set the negative ratio of the tread within a range of 68 to 85% and the Tr curvature ratio within a range of 0.23 to 0.45.
[0091]
As a result, the pneumatic tire for the rear wheel can obtain high traction characteristics and a lateral grip that are preferable for the rear wheel, and can efficiently transmit the engine power to the road surface.
[0092]
If the negative ratio of the tread is less than 68% in the pneumatic tire for the rear wheel, high performance as compared with the conventional one can be obtained, but the above-described action suitable for the rear wheel cannot be sufficiently obtained.
[0093]
On the other hand, in a pneumatic tire for rear wheels, if the negative ratio of the tread exceeds 85%, the absolute ground contact area is insufficient, and the required steering stability cannot be obtained.
[0094]
Next, in a pneumatic tire for a rear wheel, if the Tr curvature ratio is less than 0.23, a bank angle necessary for the rear wheel cannot be secured (a flat shape). Also, when you ride the bike, the ground contact surface decreases from a certain angle.
[0095]
Further, in the pneumatic tire for the rear wheel, when the Tr curvature ratio exceeds 0.45, the ground contact area during the straight traveling is reduced, and the rear wheel that is the driving wheel has insufficient traction.
[0096]
The pneumatic tire 10F of the present embodiment has a bias structure, but may have a radial structure. By making the tire structure radial, when the load load is set to be equal, the tire mass can be reduced compared to the bias tire, the handling lightness can be improved compared to the bias tire, and the unsprung load can be reduced. it can.
[0097]
Also, in the case of radial tires, because of the structure, the grip characteristics of the tread surface part are improved, so the strain that the block bears increases, and there is a tendency to be disadvantageous against chipping of the block compared to the bias tire, By optimizing the shape of the block as in the present embodiment, it is possible to achieve both improvement in steering stability and securing of block durability.
[Other Embodiments]
In the embodiment described above, the side wall surface 16 includes the two groove wall portions of the first groove wall portion 16A and the second groove wall portion 16B having different inclination angles on the tread surface side of the base curved surface 16C. Not only this but as shown in FIG. 6, you may provide the 3 or more groove wall part from which an inclination angle differs.
[0098]
When the side wall surface 16 includes a plurality of groove wall portions having different inclination angles, and the inclination angles of the groove wall portions are α, α1, α2, α3,. The groove wall portion with the inclination angle αn connected to the root curved surface 16C and the groove wall portion with the inclination angle αn−1 satisfy the relationship of αn> αn−1, and −10 ° ≦ α ≦ 20 °, αn ≧ α, and 0 ° ≦ αn ≦ 30 °, the height H of the block 14, a groove wall portion with an inclination angle α, and a groove wall portion with an inclination angle α1 It is preferable that the relationship with the height h of the boundary portion satisfies 0.2H ≦ h ≦ 0.8H.
[0099]
By setting αn ≧ α, the block has a divergent shape, and high land rigidity is obtained.
[0100]
By setting 0 ° ≦ αn ≦ 30 °, high block rigidity can be obtained.
[0101]
Next, when αn <αn−1, the block rigidity of the base is lower than the rigidity of the surface layer portion, and cracks are easily generated.
[0102]
Next, when 0.2H> h, the required block rigidity cannot be obtained, and the entire block becomes weak.
[0103]
On the other hand, when 0.8H <h, the block rigidity of the tread portion increases, and steering stability cannot be obtained.
[0104]
Next, when −10 °> α, the rigidity of the tread portion is too weak, and the feeling of rigidity necessary for steering stability is insufficient.
[0105]
On the other hand, when α> 20 °, the edge effect is reduced and steering stability cannot be obtained.
[0106]
Next, when αn <α, the base block rigidity becomes lower than the rigidity of the surface layer portion, and cracks are likely to occur.
[0107]
Next, when 0 °> αn, there is a risk of block missing due to insufficient block rigidity.
[0108]
On the other hand, when αn> 30 °, the block rigidity becomes unnecessarily large, and steering stability cannot be obtained.
[0109]
In the above embodiment, the shape of the tread surface of the block 14 is rectangular, but the shape of the tread surface may be other than a rectangle.
(Test example)
In order to confirm the effects of the present invention, tires (test types 3 and 4) of the examples to which the present invention was applied and tires of conventional examples (test types 1 and 2) were prepared and applied to actual vehicles equipped with the test tires. Thus, tests on traction, side slip, gap passage property, and chipped block were conducted.
[0110]
The test was performed on rough terrain, and the evaluation was a 10-point scale evaluation by a test rider. The larger the value, the better the performance. In addition, in this test, 7 points or more are set as passing points.
[0111]
The tire structure is as described below.
Pneumatic tire for front wheels: has two carcass plies with a bias structure made of nylon cord (cord crossing angle 30 °) and one breaker made of nylon cord. The tire size is MCR 80 / 100-21, the internal pressure is 80 kPa, and the load is equivalent to one passenger.
Pneumatic tire for rear wheel: has two biased carcass plies made of nylon cord (cord crossing angle 30 °) and one breaker made of nylon cord. The tire size is MCR 110 / 90-19, the internal pressure is 80 kPa, and the load is equivalent to one passenger.
Test type 1: As shown in FIG. 7, a pneumatic tire provided with a block whose side wall surface has a constant inclination angle (α) from the tread surface side to the groove bottom (excluding the root curved surface). No chamfering at block corners.
Test type 2: A pneumatic tire provided with a block whose side wall surface has a constant inclination angle (α) from the tread side to the groove bottom (excluding the root curved surface). The inclination angle is different from that of test type 1. No chamfering at block corners.
Test type 3: As shown in FIG. 4 (A), a pneumatic tire provided with a block having two groove wall portions with different inclination angles on the side wall surface.
Test type 4: As shown in FIG. 8, a block having three groove wall portions (first groove wall portion 16A, second groove wall portion 16B, and third groove wall portion 16D) whose side wall surfaces have different inclination angles is provided. Pneumatic tires.
[0112]
[Table 1]

From the test results, the pneumatic tire to which the present invention is applied is superior in the durability of the block as compared to the conventional example, and has high performance in terms of traction, skidding, and gap passage. I understand.
[0113]
The pneumatic tire for the rear wheel has a radial structure (tire size: MCR 120 / 90R18. It has one radial carcass ply made of nylon cord and two belt plies made of aramid fiber cord). A similar test was performed, but the results were exactly the same.
[0114]
【The invention's effect】
As described above, according to the pneumatic tire and the mounting method of the pneumatic tire of the present invention, the edge effect of the land portion within the contact surface is ensured, and the land portion root is secured without impairing the rigidity of the land portion. It has the outstanding effect that the crack resistance of a part can be improved.
[Brief description of the drawings]
FIG. 1 is a development plan view of a tread of a pneumatic tire for a front wheel according to an embodiment of the present invention.
2 is a cross-sectional view taken along the rotation axis of the pneumatic tire shown in FIG.
FIG. 3 is a perspective view of a block.
4A is a longitudinal sectional view showing a side wall surface of a block, and FIG. 4B is a sectional view of a corner portion (ridge line portion) of the block.
5A is a cross-sectional view parallel to the tread surface of the block passing through the first groove wall portion, and FIG. 5B is a cross-sectional view parallel to the tread surface of the block passing through the second groove wall portion; ) Is a cross-sectional view parallel to the tread surface of the block passing through the circular arc curved surface.
FIG. 6 is a cross-sectional view of a pneumatic tire block according to another embodiment.
FIG. 7 is a cross-sectional view of a block of a pneumatic tire according to a conventional example used in the test.
FIG. 8 is a cross-sectional view of a pneumatic tire block according to an example (test type 4) used in the test.
9A is a perspective view of a block before chamfering, FIG. 9B is a sectional view taken along line 9 (B) -9 (B) of the block shown in FIG. 9A, and FIG. It is a perspective view of the block after chamfering, (D) is a 9 (D) -9 (D) sectional view taken on the line of the block shown to FIG.9 (C).
[Explanation of symbols]
10F pneumatic tire
12 tread
14 blocks (Land)
16 Side wall surface
16A First groove wall
16B Second groove wall
16C root surface

Claims (7)

A pneumatic tire having a land portion defined by a plurality of grooves intersecting each other in a tread and having ridgelines formed at corners of the land portion formed by side wall surfaces and side wall surfaces adjacent to each other of the land portion. ,
The side wall surface has an arcuate root curved surface having a center of curvature on the outer side of the land portion on the groove bottom surface side and smoothly connected to the groove bottom surface,
The base corner portion formed by the pair of base curved surfaces of the land corner portions is formed into a substantially smooth curved chamfered shape, and the side wall surface excluding the base curved surface is defined as the land portion. A pneumatic tire, characterized by being located on the outer side of the land or coincident with a virtual ridgeline defined by a corner and a virtual side wall surface obtained by extending toward a groove bottom surface. The tread negative ratio is set within the range of 65-97%,
The tread width measured along the tread axis of rotation is defined as Tw, the distance measured along the tire radial direction from the tire equatorial plane position to the tread edge on the tread is defined as TH, and TH / Tw is defined as the Tr curvature ratio. Sometimes, the Tr curvature ratio is set within a range of 0.20 to 0.50,
The side wall surface has a plurality of groove wall portions with different inclination angles with respect to a normal line perpendicular to the tread surface in the groove depth direction, and the inclination angles of the groove wall portions from the grounding side toward the groove bottom side are α, α1. , Α2, α3... Αn−1, αn, a groove wall portion having an inclination angle αn connected to the root curved surface and a groove wall portion having an inclination angle αn−1 are expressed as αn> αn. −1 and further satisfy −10 ° ≦ α ≦ 20 °, αn ≧ α, and 0 ° ≦ αn ≦ 30 °,
When the height of the land portion is H and the height of the boundary portion between the groove wall portion with the inclination angle α and the groove wall portion with the inclination angle α1 is h, 0.2H ≦ h ≦ 0.8H is satisfied,
The land corner formed at least by the groove wall having an inclination angle αn is formed in a curved chamfered shape following the land corner formed by the root curve. The pneumatic tire according to claim 1. The tread negative ratio is set within the range of 75-97%,
The pneumatic tire according to claim 1 or 2, wherein the Tr curvature ratio is set in a range of 0.23 to 0.45. The tread negative ratio is set in the range of 68-85%,
The pneumatic tire according to claim 1 or 2, wherein the Tr curvature ratio is set in a range of 0.23 to 0.45. The pneumatic tire according to any one of claims 1 to 4, wherein the pneumatic tire has a radial structure. A pneumatic tire mounting method, wherein the pneumatic tire according to claim 3 is used for a front wheel of a motorcycle and the pneumatic tire according to claim 4 is used for a rear wheel of the motorcycle. The method for mounting a pneumatic tire according to claim 6, wherein the pneumatic tire has a radial structure.

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